This invention relates generally to an insulated, gas tight door for use in high temperature industrial applications, such as on boilers, economizers, scrubbers, precipitators, bag houses, flue gas ducts, etc., and in particular, to door systems for selective catalytic reactor (SCR) systems. SCR systems use catalyst material held in containers to reduce nitrogen oxides from flue gas, such containers being periodically transported into and out of the SCR structure to replenish the catalyst as necessary.
Access doors for industrial applications have been patented and, for example, are disclosed in U.S. Pat. Nos. 4,574,973; 4,685,586; and 5,158,043. Such doors were initially developed to eliminate door leakage and cold spots, which could cause inside acid condensation and resulting corrosion, and to provide fast and adequate access for internal maintenance of such equipment. Other types of doors have since been developed to provide other features in different applications for flue gas.
However, a need exists for a door which provides a tight seal for a high temperature industrial application, such as for a SCR system, and which facilitates transport of equipment and supplies, such as containers of catalyst, into and out of such industrial application.
It is, therefore, the principal object of this invention to provide an industrial door system for high temperature applications.
Another object of the present invention is to provide a door system for a selective catalytic reactor (SCR) system.
A further object of the present invention is to provide a door system which can be readily installed on a casing wall and with a door opening having variances in the dimensions of such door opening.
A still further object of the present invention is to provide a door for an SCR system using a davit arrangement.
Yet another object of the present invention is to provide a door for a SCR system which allows for heavy catalyst containers to be transported into and out of a SCR structure.
Generally, the present invention includes an SCR catalyst door having a flat and somewhat flexible door plate with notches around the edge thereof for receipt of swing bolts which are attached to a door frame. The door plate may include interior insulation and is suspended from a davit assembly mounted on the casing wall of the SCR structure adjacent to the door.
A sealing gasket is provided around the perimeter of the door plate, such gasket being flexible to provide a tight seal of the door against the door frame, even upon the occurrence of some warpage of the SCR system casing wall and/or the door frame. Preferably, the sealing gasket is square in cross-section, and is comprised of braided ceramic material. Such gasket is seated between stainless steel retainers provided about the edges of the door plate. These gasket retainers are placed in a dove-tail pattern which accommodate the expansion of the gasket, once the gasket is compressed in a sealing relationship. By capturing such expanded portion of the gasket, the retainers reduce the likelihood that the gasket will work loose when the door is opened.
The lower edge of the door extends downwardly below the floor level of the SCR system floor, and the lower edge of the door opening is typically flush with the floors on the inside and outside of the SCR building.
The door is generally attached to exterior of the SCR casing, and because personnel, wheeled carts and other vehicles may be required to enter the opening of the SCR system periodically, a landing, or platform, typically extends outwardly from the exterior of the building adjacent the door. Such platform may include a well, or recess, along the lower edge of the door opening into which the lower edge of the door is received.
A problem arises, however, in that in order to swing the door open in a conventional manner, such as by using conventional hinges at the edge of the door, the door would only be able to move to the boundary of the recess and would thus be blocked from opening fully. Accordingly, the door of the present invention includes a davit assembly modified to allow the door to be easily lifted by a predetermined amount in order to rise upwardly and out of the recess, to therefore allow the door to swing over the platform to a fully open position.
Closing of the door is accomplished in the reverse manner by swinging the door over the recess, and then lowering it back into place with the davits such that the lower edge of the door extends into the recess, below floor height. The door is then resealed against the door frame.